The invention concerns a vacuum cleaner head for a vacuum cleaning machine with a housing having a connection tube to the suction aggregate of the vacuum cleaning machine in order to produce an airflow. A rotary roller brush is mounted in the housing close to its suction opening. The bristles of the roller brush project outwardly through the suction opening when the roller brush is in its lowest position. An air turbine is mounted in a turbine chamber of the housing in such a way that the air turbine can be acted upon by the flow of air drawn in, for which purpose an inflow opening is provided in the turbine chamber through which the flow of air drawn in can be directed onto the air turbine.
Vacuum cleaner heads usually comprise a housing with a connection tube to provide the airflow generated by the suction aggregate of a vacuum cleaning machine, and a rotary roller brush mounted in the housing close to its suction opening. In their lowest position the bristles of the roller brush project outwards through the suction opening and can therefore brush the surface beneath, which is to be vacuum cleaned. The roller brush is often driven by an air turbine acted upon by the flow of air drawn in.
Owing to their simple structure, air turbines are often used in central exhaust units and in machines for commercial cleaning, since such vacuum devices have powerful fans. Because of the high drive power, such vacuum cleaning machines present an accident risk to the person operating the machine or to people nearby, which should not be underestimated. When the vacuum brush is lifted clear of the surface being cleaned while the suction unit is still operating, the suction opening with the rapidly rotating brush is exposed. Since there is no longer any load, the rotation speed of the turbine and, of course, that of the brush as well increases rapidly, and any contact with the brush can lead to injury.
In such vacuum cleaner heads there also generally occurs the problem that when the vacuum cleaner head is lifted clear of the surface being cleaned beneath it, the rotation speed of the roller brush increases since there is no longer any force on it. The rotation speed increase applies not only to the roller brush but also to the air turbine driving it, and this not only leads to considerable stressing of the turbine bearings but also greatly increases the level of noise emitted.
To avoid these disadvantages, in DE 33 08 294 A1 an arrangement with an alternative air path has already been proposed, which circumvents the turbine chamber in the manner of a bypass so that when the vacuum cleaner head is lifted clear of the carpet or the like, the alternative air path is automatically opened.
DE 40 36 634 A1 describes a dust-sucking mouthpiece which comprises a rotary roller brush. In this dust-sucking mouthpiece there is a braking device which acts on the roller brush or its drive system and which can be released from its braking position depending on whether or not the mouthpiece is resting on a surface to be cleaned.
From DE 42 29 030 A1 a vacuum cleaner head is known, which comprises a roller brush driven by an air turbine. To avoid a drastic increase in rotation speed when the roller brush is raised, a throttle element for the airflow drawn in is provided, which when the vacuum cleaner head is lifted clear of the surface being cleaned, throttles the airflow drawn in until the roller brush comes almost or completely to rest.
The objective of the present invention is to provide a vacuum cleaner head of the aforementioned kind, in which the turbine rotation speed can be adapted automatically to the power demand of the roller brush at any time.